The invention relates to a method for generating a control program for ophthalmologic surgery, to control programs for ophthalmologic surgery, to a computer for controlling an ophthalmologic laser system, and to a data medium having control programs for ophthalmologic surgery.
The invention will be explained below with a view to the known LASIK method.
In the ophthalmologic LASIK method, undesired imaging properties of the eye are removed or at least reduced by reshaping the cornea.
Conventionally, in the LASIK method, a so-called flap is formed on the front side of the cornea and folded to the side. In a second step, corneal tissue is removed according to a so-called ablation profile in the stroma thus exposed. The flap, which has remained joined to the cornea at a so-called hinge, is then folded back and relatively rapid healing of the tissue takes place.
In order to generate the flap, essentially two techniques are currently available: On the one hand, an oscillating blade is mechanically guided through the corneal tissue with a so-called microkeratome in order to form the flap.
According to a more advanced method, a laser is also used for generating the flap. To this end in particular FS lasers (femtosecond lasers) are used, the radiation of which is focused in the stroma below the surface of the cornea so as to photodisruptively cause tissue separation at a multiplicity of adjacent positions there. This photodisruptive process is also referred to as LIOB (Laser-Induced Optical Breakdown) (cf. Juhasz et al. “CORNEAL REFRACTIVE SURGERY WITH FEMTOSECOND LASERS”, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No 4, July/August 1999). If the focusing of the laser pulses leads to a sufficient power density (energy per unit time and area), which lies above a particular threshold value, then the photodisruptive process takes place with sufficient quality i.e. smoothness of the cut and accuracy in respect of the desired shape. In order to achieve the high intensities necessary for this, ultrashort laser pulses are generally required i.e. laser pulses in the femtosecond range, this term conventionally covering pulse lengths shorter than one picosecond i.e. pulse lengths of between 1 femtosecond and 999 femtoseconds. The focusing of the laser beam is then generally carried out in the micrometer range.